Digital audio provides significant benefits over traditional analog audio recording, including more ease and precision in editing, easier addition of special audio effects, and the elimination of sound quality degradation in successive generations of recordings. Digital audio can also be stored in a computer memory and read directly to provide instant random access to any point on the program, For all of these reasons, digital audio workstations are common in the video and film industries.
The basic process of editing a video or film program with digital audio generally begins with the production of a video program with preliminary audio tracks. The program is then taken to a digital audio workstation, where more tracks are added, sound effects are built, and the existing tracks are cleaned up. At this stage, in contrast with the first, video-based stage, the audio editing is done in a more narrow and precise time frame than the one-thirtieth second period of an individual video frame or the one twenty-fourth second period of a film frame; therefore, the editing is known as "sub-frame" editing. Finally, in the last stage of the audio production, the program receives the final mixing and "sweetening" of the audio tracks.
It is the second and final stages of this process in which the invention is most useful. Those stages and the sub-frame precision they require , necessitate close interaction of the audio editing with the video portion of the program. The editing typically requires, among other things, synchronization of the audio effects with the action in the video program. As noted above, if the digital audio program is stored in a computer memory, it can be accessed immediately, greatly facilitating this editing process. (United Kingdom patent Application No. 2,245,745 discloses an application of this capability.) However, with current systems the video program is stored on a normal video tape recorder, which requires a great deal of time to rewind or fast-forward to the desired editing point and must be pre-rolled to its full speed for precise editing. Hence, the potential editing speed and convenience of the digital audio process is held back by the use of conventional video recording.